debian/rules: fix reproducibility with varying locale
debian/rules: fix reproducibility with varying locale

The generated svtplay zip file was showing differences when built using
a US locale vs a French locale. Fix this by overriding LC_ALL with
C.UTF-8 as suggested by Debian's Reproducible Builds project. This issue
was discovered thanks to their automated (re)build infrastructure.

Reference: https://wiki.debian.org/ReproducibleBuilds/Howto#Files_in_data.tar_vary_with_the_locale

olof/debian-svtplay-dl,olof/debian-svtplay-dl